New Sampling Method And Applicability Test Of Shallow Low Moisture Content Undisturbed Gravel Soil

Gravel soil has many advantages,such as good compaction,high filling density,high shear strength,high bearing capacity,small deformation and strong permeability.It is widely used in water conservancy,power,railway,transportation,industrial and civil construction industries.The samples used in laboratory tests are generally disturbed gravel soil or remolded gravel soil.In order to study the physical and mechanical properties of gravel soil and solve the problems of high disturbance rate,low success rate and high breakage rate in transportation of undisturbed gravel soil,a sampling method of undisturbed gravel soil suitable for shallow layer and low water content is explored based on a temporary cementing material.The density,specific gravity,volume change and volatility of menthol were studied.The feasibility and applicability of menthol as temporary cementing material for undisturbed gravel soil samples were analyzed.The cementing,sampling and removal process of menthol for gravel soil was completed.Through the compression,vibration and impact tests of peppermint cemented gravel soil samples,the relationship between the anti-interference ability of the samples taken by this sampling method and the temperature and particle size of the samples was analyzed.It was found that the undisturbed gravel soil samples taken by this sampling method had high anti-pressure,anti-vibration and anti-impact ability,and solved the problems of disturbance and damage of the samples during transportation.Through indoor volume shrinkage,direct shear and compression tests,the influence of menthol on the volume size and physical and mechanical parameters of gravel soil is analyzed from a macroscopic point of view.It is found that the volume expansion rate of gravel soil with different particle sizes and dense states(0.009%~0.411%)by menthol sampling method is much lower than that of gravel soil with in-situ controlled drainage freezing method(0.631%~1.472%).The physical and mechanical parameters such as shear strength,internal friction angle,void ratio,compression coefficient,compression modulus and compression index of samples cemented and volatilized by menthol have no significant influence on the physical and mechanical parameters of samples manually prepared in the same batch.The perturbation evaluation criteria of menthol on sand samples are given.With the help of CT scanning results,the influence degree of menthol on particle movement,porosity and morphological characteristics of sand-gravel soil was analyzed from a mesoscopic point of view.The influence direction and range of menthol on the spatial position of particles in sand-gravel soil were obtained.It was proved that there were no porosity and morphological characteristics(size,contour shape,angularity)before and after menthol was injected into sand-gravel soil samples.Significant influence and significant correlation.Based on the above research,the sampling method of undisturbed gravel soil is put forward,the control standard procedure of undisturbed gravel soil sampling is established,and the specific sampling steps are given.